What is a borehole, and how does it work?

Part of our well and borehole water guide

A neighbour says their water comes from a borehole, or a house listing mentions one. Is it just a deep well, and how do you check what reaches your tap, for instance with a 20-in-1 strip?

By Andrew Tomlinson, WaterKit · Last reviewed 29 October 2026

What is a borehole?

A borehole is a groundwater source where water is pumped from deep underground, according to the Drinking Water Inspectorate (DWI). The British Geological Survey (BGS) defines an aquifer as a rock formation porous and permeable enough to yield a significant quantity of water to a borehole, well or spring.

A well is a close cousin, but the DWI treats it differently. It says wells and springs, although derived from groundwater, are very often influenced by surface water, so it considers them surface water for water quality risks. Our well and borehole water guide covers drinking and testing in full.

Where does borehole water come from?

From rain and snowmelt that soak down into rock. BGS defines groundwater recharge as the inflow of water to a groundwater body from the surface, and says infiltration of precipitation and its movement to the water table is one natural form.

In its groundwater resources page, BGS says groundwater provides approximately a third of public water supply in England, and that the Chalk and the Permo-Triassic sandstones are the major sources. That is the mains side, covered in where your tap water comes from.

How does a borehole work?

Water flows from the aquifer into the shaft and a pump brings it to the surface, then pipes carry it on. The DWI's example of a supply to a single home runs from a spring chamber or borehole through pipes and an ultraviolet treatment unit into a loft tank, and notes that all installations will vary. A larger example sends it first to raw water storage tanks.

Pumping lowers the water level in the aquifer around the shaft, which is the drawdown in the table. BGS describes a pumping test as pumping water out of an aquifer and measuring the effect on water levels. The DWI suggests raising the borehole head-works at least 0.5 metres above ground level, to keep surface water and spillages out. It also suggests sealing abandoned boreholes. The sources we read do not describe a household borehole's casing or pump, so ask a driller about those.

How deep is a borehole?

As deep as it takes to reach water, and we found no UK official figure for a typical household borehole. The one depth marker in the sources we read is in the Water Resources Act 1991, section 198, which applies to England and Wales. It sets a notice duty for a well or borehole intended to reach more than fifty feet, about 15 metres by our conversion.

How do you get a borehole, and what does the law ask?

Start with the notice duty. Section 198 says anyone proposing to sink a well or borehole to search for or abstract water, intended to reach more than fifty feet, must give notice to UK Research and Innovation (UKRI) before beginning. The person sinking it must also keep a journal of the work, including the strata passed through and the levels where water is struck and rests. On completion or abandonment they send a copy to UKRI, with the particulars of any flow test.

That is only the drilling notice. Taking the water, and any planning permission, are separate matters that differ by nation, and we have not covered them here. Our guide to drilling a borehole in your garden picks them up.

Why might the water at my own tap differ from what I expect?

Because a borehole is a private supply, and a figure for an area, or for a neighbour's borehole, does not tell you what comes out of your own tap. The DWI's private supply categories include a single premises supply from a borehole. It says the local authority may monitor those supplies, and must do so if the owner or occupier asks. Several things between the aquifer and your glass can differ from house to house.

• The source itself. The DWI says groundwater pathogens have had longer to die off than those in surface water. It adds that where a hazard is natural or persistent, some treatment is needed in most cases.
• Pipes and tanks. The DWI lists replacing corroded or deteriorating pipework, inspecting storage tanks, and stopping water stagnating in them. It also lists replacing lead pipework. Our loft tank guide explains the tank side.
• Treatment upkeep. The DWI says filters, lamps and filter media should be replaced to the manufacturer's instructions.
• The season. BGS says groundwater levels are generally highest in early spring and lowest in early autumn.

“If you're on a borehole, I wouldn't lean on a neighbour's water or an area figure, because your own pipes, tank and treatment sit between the aquifer and your glass. Testing at the tap you actually drink from is the sensible way to see what reaches you.”

Because these vary, a single reading in a dry spell and another after a wet winter can differ. A 20-in-1 strip dipped at the same tap in different seasons lets you see that for yourself.

What one reader found

In a 2019 forum thread, one poster said they had a borehole drilled about 4 years earlier in North Oxon. In their words, "They drilled to about 45 metres, sleaved, put a pump in". It also had a concrete ring and manhole cover, cost about £7k plus VAT, and had caused no issues since. Another poster relayed a drilling firm's view that cost depends heavily on ground conditions and the depth needed to hit water. This is one person's account, not a typical cost or depth. Shared on PistonHeads.

How can I check the water from my borehole?

Test it at the tap you drink from. Fill a clean glass or cup, dip one strip, wait 30 to 60 seconds and match the pads to the chart, or enter the colours in our free results checker. The WaterKit Water Test Kit also has an optional rapid coliform bacteria test, read after 24 to 48 hours. Our water testing guide and bacteria testing guide give the steps. This is our reading of the chart.

• Nitrate. Steps at 25, 50 and 100 mg/l.
• Manganese. Steps at 0.05, 0.1, 0.5 and 1 mg/l.
• Iron. The first colour step sits above the UK limit, so a zero reading means none detected at that step, not none.
• Hardness. Steps at 0, 25, 50, 100, 250 and 425, with the unit basis unconfirmed, so treat it as a rough comparison.

Compare nitrate, manganese and iron with the limits in the well and borehole guide. The bacteria test is a presence screen, not a count. The strip cannot read lead at the UK limit, so see how to tell if your house has lead pipes. A strip result is not a legal sample and says nothing about the borehole's depth, yield or construction. If the strip points to a problem, how to treat well or borehole water is the next read.

Any figure for your area, or for a neighbour's borehole, is an average, and your own tap can differ because the DWI lists pipework, storage tanks and treatment upkeep as things that vary from house to house, and BGS says groundwater levels swing between early spring and early autumn. The pads that matter most here are nitrate, manganese and iron, and a step up at one of them between a spring and an autumn test would be a prompt to look at the source, the pipes or the treatment (our reading of the chart, not a diagnosis). Best pack: 20 strips, enough for an early spring and an early autumn check with strips to spare for repeats (the pairing is our suggestion, based on BGS's seasonal levels), £5.99 (or £10.99 with a bacteria test), with free 2nd Class delivery on every order. See the kit

Your borehole and well questions

What is a borehole?

A shaft that reaches an aquifer, which the DWI calls a groundwater source where water is pumped from deep underground.

How does a borehole work?

Water enters the shaft from the aquifer and is pumped up, then piped on, sometimes through storage tanks and treatment, according to the DWI's examples.

What is a water borehole?

A borehole sunk to abstract water. Section 198 of the Water Resources Act 1991 refers to sinking a well or borehole for searching for or abstracting water.

Where does borehole water come from?

Rain and snowmelt that infiltrates the ground and is stored in an aquifer. BGS calls the inflow recharge.

How deep is a borehole?

It depends on where the aquifer is, and we found no UK official figure for a typical depth. Fifty feet is the notice marker in England and Wales, and the reader above reported about 45 metres.

How to get a borehole?

Give UKRI notice first if it is meant to pass fifty feet in England or Wales, then follow our drilling guide for permissions.

Can you drink water from a borehole?

The DWI says the council must monitor a single home's supply if the owner or occupier asks. Our well and borehole guide sets out the testing routes.

What is well water, and where does the water in a well come from?

Groundwater taken from a well. BGS says the still water level in a well in an unconfined aquifer is the water table, and the DWI says wells are very often influenced by surface water.

How does a water well work?

BGS says a well reaches the water table, and in an artesian (confined) aquifer the pressure can lift water above the level where it was first found. We found no UK official page on how a household well is built.

Can a well run out of water?

Yes. BGS says groundwater droughts show as lower than average water levels in aquifers, boreholes and wells. They can develop if rainfall is reduced over one or successive winters.

Sources

1. Drinking Water Inspectorate, Protecting your private water supply (borehole as groundwater source, wells and springs as surface water, headworks, abandoned boreholes, pipework, tanks, treatment upkeep; undated page; read 29 October 2026).
2. British Geological Survey, Glossary (aquifer, water table, recharge, yield, drawdown, pumping test, artesian; undated page; read 29 October 2026).
3. British Geological Survey, Groundwater resources in the UK (about a third of public supply in England, Chalk and Permo-Triassic sandstones; undated page; read 29 October 2026).
4. British Geological Survey, Drought (groundwater drought and lower levels in boreholes and wells; undated page; read 29 October 2026) and Frequently asked questions (groundwater levels highest in early spring and lowest in early autumn; undated page; read 29 October 2026).
5. Drinking Water Inspectorate, Types of private supplies (England) (single premises supplies, local authority monitoring on request, example layouts; undated page; read 29 October 2026).
6. Water Resources Act 1991, section 198, information about underground water (England and Wales; notice to UKRI for a well or borehole intended to reach more than fifty feet, journal and flow test particulars; read 29 October 2026).
7. PistonHeads, Boreholes, anyone know anything about them (Homes, Gardens and DIY forum thread, 2 June 2019; one poster's account, paraphrased; read 29 October 2026).
8. WaterKit, Water Test Kit (20-in-1 strip, 30 to 60 second read, optional rapid coliform test read after 24 to 48 hours, 20 strips £5.99 or £10.99 with a bacteria test, free 2nd Class delivery on every order, 30-day money-back guarantee) and results portal. The reading of the chart steps is WaterKit's own.

Contains public sector information licensed under the Open Government Licence v3.0.